Secrecy cipher system



j@ n 4 R. E. PIERCE ET AL.

SECRECY CIPHERv SY STEM Filed Aug. 25, 1942 2 vSheets-Sheet Perry l INVENIORS4 REBlence A RY Elector C -`R. E.- MERCE Eil-AL.

SECRECY CIPHER SYSTEM Filed Aug." 25, 1942 elector E INVENToRs REBzerceWe/fry ATTORNEY 2 Sheets-Sheet 2 Lead Patented June 4, 1946 UNITED S SECRECY CBHER SYSTEM Ralph E. Pierce, Larchmont, N. Y., and Donald B. Perry, Maplewood, N. J., assignors to American Telephone and Telegraph Company,

ration of New York Applcation August 25, 1942, Serial No. 456,014

20 Claims.

This invention relates to secrecy cipher systems, and more particularly to such systems designed for use in connection with teletypewriter systems employing the Baudot code.

Heretofore it has been proposed to encipher the characters of a teletypewriter message by combining the successive characters of a message with successive characters of a key consisting of an endless series of characters arranged in an arbitrary and random manner. The Baudot code pulses sent out for each message character will then be a resultant of the Baudot pulses representing the key character superposed on those representing the character to be transmitted.

Ordinarily each character is represented by five Baudot impulses which may be either marking or spacing, and the identity of the character is determined by the successive arrangement ofthe pulses as to their marking or spacing condition. If a pulse of a message character to be transmitted is -marking and the corresponcng pulse of the key character is also marking, then a marking pulse will be sent out. If both pulses are spacing, a marking impulse will be sent. If, however, one impulse is marking and the other spacing, then regardless of which is which, a spacing impulse will be sent out.

If, as has been heretofore proposed, the key pulses are derived from a random succession of enciphering characters recorded on a teletypewriter tape of such length that all of the messages ever sent would not use all of the enciphering characters so recorded, each message sent out would be scrambled to such extent that it would be impossible to` decipher it without knowing what key characters were employed and in what order. If the key characters were arranged in an absolutely random manner, there would be no way of predicting when a given character would be repeated, and no way to determine in what succession the key characters followed each other. With a message enciphered in this manner it would be impossible to break the code. At the receiving machine an identical key is provided which combines with the scrambled signals on the line to return the message to plain text.

As a practical matter, however, the ideal conditions for complete security mentioned in the preceding paragraph may not always be necessary or desirable. To meet these conditions it is necessary to have at'each end of each circuit duplicate random keys with as many characters as there are in all of the plain text messages to be transmitted. Consequently it is desirable to use compromise measures involving simpler are rangements. In view of the difcult problems involved, recourse has been had in the past to the expedient of using a key tape in the form of an endless belt of considerable length, so that the succession of key characters is not repeated until a considerable interval has elapsed. In order to lengthen the interval during which no repetition of the arrangement of the scrambling characters will occur, it has been proposed to use two endless key tapes, each with a different successive arrangement of characters, and each having recorded thereon a different number of characters. Each character on one tape is combined with a character upon the other tape, and the resultant set of Baudot impulses is used to encipher the Baudot impulses of the actual message character to be transmitted. lSince the Vnumber of characters 'on each tape is different, a repetition will not occur when all of thecharacters on one. tape have been transmitted and it starts again with the iirst character in vthe series. This is for the reason that the rst character will now be combined with a diierent character on the second tape from that with which it was previously combined. Therefore, no repetition will occur until a number of characters have been transmitted which is a product of the numbers of characters on the two tapes.

Whether the enciphering system is one using a single tape or one using two tapes combined,

the teletypewriter at the receiving station is soV arranged that it combines the enciphered message transmitted by the sending station with enciphering characters recorded upon tapes exactly like those used at the transmitting station. Each set of the resultant Baudot code impulses will correspond to that representing the original character of the message transmitted.

In combining two Baudot codes one with another, various methods may be used. The method most commonly used is that previously referred to, in which two like impulses combine to produce a marking pulse, and two unlike impulses produce a spacing pulse. For example, if the character desired to be transmitted is represented by the code combination mark-mark-space-mark-space, and this character is enciphered at the transmitter by being comsultant character printed at the receiving station will be that represented by mark-markspace-mark-space, which, it will be observed, is the original message character. Anyone tapping `the line, however, will get the character represented by space-mark-space-niark-mark.

With an enciphering or deciphering arrangement employing either a single key tape or two combined key tapes, it is desirable to change the settingof the tapes before an actual repetition of the order of characters occurs. This may be done by the parties at the transmitting and receiving stations having a previous understanding as to the points in the key tapes at which rnessages will start from timer to time. A different starting point in the key tape may be used for each message, or the tapes may be reset to start at a new point after a certain amount of` time has elapsed. If the new settings are agreed upon in advance, it would be very diiiicult for an unauthorized person to break the cipher. When the messages are transmitted more or less continuously, day in and day out over a long period of time, it is practically impossible to agree in advance upon the settings. Therefore, it becomes necessary for one station to advise the other as to the point at which the enciphering tapes are to be reset before each change in setting occurs. This information would, of course, be sent in cipher form. Hence there is little or no likelihood that it would furnish a clue which could be used in an attempt to break the cipher.

These resettings of the tapes at the transmitting and receiving stations necessarily occur frequently, and it is `very difficult and cumbersome to reset a tape. provide some method of producing enciphering combinations which will readily permit resetting the enciphering apparatus to start the series of key characters at a new point. In accordance with the present invention, therefore, it is proposed to use a series of selector switches instead of one or more tapes to provide the enciphering code combinations.

Speci'allv a step-by-step selector switch hav ing a large number of contacts on each of vits banks is used in lieu of a tape. In the case herein illustrated the number of contacts on each bank is twenty-two, but it may be a larger or smaller number as desired. Six banks of contadas altogether are provided for each switch, five being used to produce the elements of the Baudot code (of which there are five for each key character), while the sixth bank is used for indicating purposes, as will be described later.

Each one of the five banks of each switch or selector is used to determine one of the five impulses of the Baudet code combination. Each of the contacts in a given bank is activated in one of two ways corresponding to marking or spacing. For example, each contact may be activated either by a connection to a positive source o-r by a connection to a negative source. If preferred, some of the contacts may be connected to a source of any polarity, and the others may be made dead or idle contacts. Still another possibility 'would be to ground some contacts and connect others to battery. The contacts in each bank are in any event activated in a purely random manner in one or the other of the two possible ways provided by the plan.

If only one switch were employed to form the enciphering code combinations, the 'combination of its wipers to corresponding contacts in the five banks would determine the five pulses Consequently, it is desirable to of the enciphering code. After each code combination has been transmitted, the wipers of the switch would then be moved to the next contact on each bank to produce a new enciphering code, etc. A switch thus arranged would be equivalent to an endless tape having a number of characters recorded upon it equal to the number of positions of the switch.

Inasmuch, however, as each switch bank has only a limited number of contacts (in the case assumed twenty-two), it is desirable to employ a series of switches each having five banks of contacts, so that the resultant code combination will be determined by the combined action of all o the switches. In such case the setting of the rst and second switches in the series at any given time may be used to determine a set of five Baudet code units. These units in combination with the setting of a third switch may in turn produce another set of ve Baudot code units. This second set of Baudot code units might, when combined with the setting of a fourth switch, produce a third set of Baudot code units, which in turn combine with the setting of a yfifth switch to determine a fourth combination of Baudot code units, and so on for any desired number of switches. Various other ways may be devised for using circuits extending from switch to switch, or controlled by a series of switches, to determine Baudot code combinations for enciphering purposes. In any case the set of Baudot code units so produced may then be used to scramble the character to be transmitted, after which a new code combination may be produced by advancing one or more of the switches to its next step.A

1f, for example, the first switch is stepped to" a new setting after each code combination has been transmitted, and the second switch is arranged to take one step each time the first switch has stepped through a complete rotation, the Baudot code combinations set-up on the five banks of the first switch will, after each has been combined with a code combination determined by the second switch, be combined with a different Baudot code combination set up by the second switch after it moves to a new position. will occur each time the second switch is advanced one step by the rst switch making a complete revolution.

The second switch may in turn be arranged s0 that when it completes one rotation it will cause the succeeding switch to advance one step. The succeeding switch may be arranged so that when it completes one rotation it will advance the next Switch one step, and so on for all of the switches. By such an arrangement ve switches, each having five banks of twenty-two contacts, is capable of producing as many as 5,153,632 Baudet code combinations before a similar sequence or repetition in the ciphering key reoccurs. f

The use of step-by-step switches in the matter above described has a great advantage over the use of perforated tapes, in that the switches may be arranged to be stepped manually by the operation of keys to any desired setting when it is desired to start enciphering from a new setting. An arrangement of switches such as above described also has the advantage that, if each switch is provided with an additional bank of contacts and a lamp is connected to' each contact thereof, the setting of each switch will be visually indicated by the lamp that is lighted when its wiper rests upon a particular contact.

Further details will be clear from a detailed description of the invention when read in connec- Tliis tion with the accompanying drawings, Figures 1 (a) and 1 (b) of which illustrate the preferred embodiment of the invention.

In the drawings RL is a receiving circuit upon which the characters to be enciphered or deciphered are impressed. This circuit terminates in a winding OWr of a receiving relay RR. Normally, when no message code combination is being received, a marking signal (which may be a closed circuit impulse) passes into the circuit RL and holds the armature of the relay RR against its marking contact, so that negative battery is connected to conductor I0. When a space signal is received the armature is shifted to its space contact and positive battery is connected to the conductor l0.

The characters, after being enciphered or deciphered in a manner to be described later, are transmitted to a distant station or a local teletypewriter over a circuit TL by means of a transmitting relay TR, which may include two operating windings OWn and OWp, and a holding winding HWt. The conductor IB, which is controlled by the receiving relay RR, is connected to the junction point II of said operating windings, and the other terminals of said windings connected to conductors I2 and I3, respectively, upon which the key pulses are applied, as will appear hereinafter.

In order to properly time the superposition of the character impulses with the key impulses, and to properly time the transmission of the combined code impulses to the transmitting circuit TL, a distributor 'ID is provided. This distributor is of the general type employed in regenerative telegraph repeaters, and has a rotating brush TB which rotates over two segmental rings. The outer ring includes eight segments, a normal segment 0 upon which the brush rests when it is not rotating, a start segment Sa, code segments l, 2, 3, 4 and 5, and a stop segment Siep. The inner ring consists of a small segment Us, connected over conductor I5 to the conductor it, and a large segment I6 connected by conductor i7 to the holding winding HWr of the receiving relay RR. The purpose of the winding I-IWr will be pointed out later. The distributor is of the start-stop type, and is released by means of a release magnet RM in response to the start impulse received from the circuit RL.

The key is produced by means of a series of selectors or switches A, B, C, D and Each selector has six levels or banks of segments or contacts, herein shown as twenty-two in number for each bank of each switch. The rst, second, third, fourth and fth levels of the switch are used to formulate the key code combinations. and the sixth level is used to control lamps for indicating the positions in the switches, as will appear more clearly hereinafter. Each selector has a wiper for each bank of contacts, and the contacts of banks or levels l to 5, inclusive, are connected either to positive or negative battery in an arbitrary and random order.

The ve brushes of selector A are connected to the brushes of selector B through relays F1, F2, F3, F4 and Fs, respectively. The armatures of said relays are connected through relays G1, G2, Gs, G4 and G5, respectively, to the brushes of selector C. The armatures of this second set of relays are in turn respectively connected through the windings of relays H1 to Ht, inclusive, to the brushes of selector D, and the armatures of the last-mentioned relays are similarly connected to the brushes of selector E through the windings of relays K1 to K5, inclusive.

Each armature of each relay of the sets F, G and H is, when attracted, connected to negative battery, and when released is connected to positive battery. The armatures of the set of relays K1 to K5, inclusive, when attracted, are connected over their front contacts to conductor I2, when released, are connected over their back contacts to conductor I3. These conductors, it will be recalled, are connected, respectively, to the windings OWn and OWp of the transmitting relay '1L The brushes of the several switches may be advanced step-by-step by means of stepping magnets Ma, Mb, Mc, Md and Me, respectively. Each stepping magnet has associated therewith a locking relay, the relay A1 being associated with' the stepping magnet Mb, the` locking magnet B1 being associated with the stepping magnet Mc, etc. A stepping cam SC associated with the distributor TD is arranged to close a contact at the time the stop impulse is being transmitted, aswill be described later. This contact completes a circuit for the stepping magnet Ma to advance the wipers of the selector A one step after each code combination has been transmitted. The operation of each' of the stepping magnets ofthe other switches is controlled by the preceding switch, as will appear later.

Each of the selectors is provided with a sixth level of contacts equal in number to those of the other levels. In the case of selectors A, B, C and D, each. of these contacts except the last one is connected through a lamp to battery, so that when the wipers of the switches are resting upon a particular contact, the lamp corresponding to that contact in the sixth level will be lighted. The last contact in the sixth level of each of these four switches is connected to a circuiit which operates the stepping magnet and the associated locking relay of the succeeding switch. A lamp is also included in the circuit of the last contact of the sixth level of each' of these switches, to indicate that the switch is inthe position corresponding to said contact. In the case of selector E, the last contact of the` sixth level is connected through a lamp to battery -just as are the other contacts of that level, and no step` ping circuit is associated with said last contact for there is no succeeding switch to be operated.` With this arrangement of stepping circuits, selector A is advanced after each character has been transmitted by the closing of the circuit over conductor I8 which controls the stepping magnet Ma. When the selector A is advanced to its twenty-second step, a circuit is completed over conductor I9 for the stepping magnet Mb of the selector B. Selector B, therefore, is advanced one step for each' rotation of selector A. When selector B has been advanced to its last contact, a circuit is likewise completed over conductor 20 for the stepping magnet Mc of the selector- C, which in turn is advanced one step for each rotation of selector B. In a similar mannerthe last contact of the sixth level of selector C controls the stepping of selector D, and the last contact of the lower level of selector D in turn controls the stepping of selector E.

An important feature of the invention is the provision of the keys Ka, Kb, Kc, Kd and Ke, which are associated with conductors I8, I9, 20, 2| and 22. By means of these keys each selector may be advanced manually step-by-step to any desired position. The operator is,` therefore, able at any time to -reset any and all switches tolnew.

.bined with the key determined by the setting of the selectors A to E, inclusive, as will appear later. If the received characters are message characters in plain text form, they Awill then be transmitted to the line TL enciphered.k If, on thev other hand, the receiving circuit RL is receiving characters already enciphered at a dis' tant station, they will be combined with the proper key combinations set up by,the selectors A to E inclusive to produce in the transmitting circuit TL deciphered characters corresponding to the original plain text message characters.

When no code combination is being received, the `circuit RL receives va continuous marking impulse corresponding to the stop signal transmitted after each code combination. Each code combination consists of a start impulse, which is always a spacing impulse, followed by live Baudot code impulses representingthe character to be transmitted. The fifth Baudot code impulse is in turn followed by a stopping pulse, which as already stated, is always a marking pulse and acts to hold the armature of receiving relay RR against its marking contact.r The five impulses of the `Baudot code may be either marking or spacing impulses, depending upon the characters which they represent. l

, Upon receiving a start signal in the form of a `spacing impulse, the winding OW; of receiving relay RR shifts the armature of said relay from marking to spacing, and plus battery iis thereby connected over conductor I to point II, and thence over conductor I to segment 14 of the inner ring of distributor TD. From this point the circuit continues over the brush TB of the distributor, over segment O ofthe outer ring of the distributor, and through the release magnet RMtO negative battery. The release magnet is accordingly operated and releases the brush arm of the distributor, so that the brush TB Vpasses from segment 0 to the start segment Sa.

yAt this time the start impulse is still being'received by the relay RR and a circuit is completed from v,positive battery, over the spacing vcontact of relay RR, over conductor It), through the operating Windingv OWp of the transmitting relay TR, over conductor 23, stop segment Stv. and brush TB to the long segment I6 of the inner ring, thence over .conductor I1 and through holding winding HWr of receiving relay RR to ground. Current now iiowsfin the holding winding of the receiving relay RR in such a direction as to holdthe armature against its spacing contact so long as the brush in the distributor remains on the start segment Su. The operating winding OWp of the transmitting relay TL is energized over the circuit above described and operates to shift the ar- I mature of the transmitting relay TL from its marking to its spacing contact, so that plus battery is connected to the transmitting circuit TL to send a start signal to the distant station.

The transmitting relay TR is provided with a holding winding HWt connected between ground Further details of the invention will be evident '8 and the amature of said relay, so that said winding receives current in a direction tending to hold the armature of relay TR upon the contact to which it was last moved until an impulse is received to shift it to the opposite contact. The holding winding l-IWrV of the relay RR, on the other hand, functions to hold the armature of the latter relay upon the contact to which it has been operated, until after the brush of the distributor moves off the contact of the outer ring of the distributor corresponding tothe impulse being received. .This prevents any possibility of the suc- A ceeding impulse shifting the armature of the receiving relay RR to its opposite contactv before the corresponding impulse has been transmitted to line LL, since the receiving winding OWr of the receiving relay RR produces a weaker pull upon the armature than that caused by the holding winding HWr.

After the brush moves away from the start segment Sa, the holding winding HWr is released and the brush passes to segment number I. In the meantime the first impulse of the Baudot code Yis being received in theoperating winding OWr of the receiving relay RR. If this happens to be a marking impulse, negative battery will be connected to conductor I I. While this pulse is being received, the brush of the distributor TD passes over segment number I of the outer ring of the distributor and the scrambling operation takes place in a manner appearing presently. By this operation the first im-pulse of the Baudot code combination will have superposed thereon an irnpulse determined by the setting of the selectors A, B, C, D and E, and specifically this superposed key impulse is determined by the first level of contacts and the corresponding brushes of said selectors. y

Let it be assumed that the selectors are in the positions shown in the drawings, i. e. the brushes of selector A upon the 6th segment, the brushes of selector B upon the 18th segment, the brushes of selector C upon the 14th segment, the brushes of selector D upon the 20th segment and the brushes of selector E upon the 14th segment. It will be evident that the relay F1 is not operated since both of its terminals are connected to negative battery over the 6th contactY of selector A, and the 18th Contact of selector B, respectively. The armature of relay F1 will, therefore, rest upon its back contact. v

It will also be evident that relay G1 is not operated, as v.plus battery `is connected to the back contact of relay F1 and the brush of selector C rests on a contact connected to positive battery.

K1 will, therefore, rest .upon its back contactv which is connected to conductor I3.

Assuming a marking signal is being received by receiving relay RR, a circuit is completed from negative battery over the marking contact of relay RR, over conductor I9, through operating.

winding OWp of the transmitting relay TR, over conductor i3, back contact of relay K1 to segment number I of the distributor TD. Thence the circuit ccntinuesrover the brush of the distributor and the long segment I6, over conductor I'I, and

through the holding Winding HW: of the receiving relay RR. Relay RR, therefore, holds its armature upon its marking contact so long as the brush oi the distributor is passing over segment number I.

It will be noted that there are two controls over the circuit above traced, one exercised by the receiving relay RR and the other by the relay K1. Inthe case assumed the rst of these controls corresponds to a marking impulse, but the control by the relay K1 corresponds to a spacing impulse. This Will result in transmitting a spacing impulse to line TL because current is transmitted through the operating winding OWp in such a direction as to shift its armature to its plus or spacing contact. If, however, the pulse received by the relay RR had been a spacing pulse, the armature of the relay RR would have been connected to positive battery and both controls would have been spacing controls. Current would then flow through the operating winding OWp in the opposite direction. This Would result in shifting the armature of the relay TR to its negative or marking contact and a marking signal would be sent to the line.

. As soon as the brush passes off segment number l of the distributor, the second impulse of the Baudot code may be received as holding winding I-IWr is deenergized. Assuming that this pulse is a marking impulse, the armature of relay RR will assume its marking position and negative battery will be applied to the conductor It. The nature of the pulse to be transmitted to the outgoing circuit TL, however, will be determined by the circuits controlled by the brushes of the second level of selectors A to E, inclusive.

If We trace through the circuits controlled by these brushes, it will be seen that relay F2 is not operated as positive battery is connected to both terminals of its winding. Relay G2 is operated as one of its windings is connected to positive battery over the contact of relay F2, and the other terminal is connected to negative battery over the Wiper of selector C. Relay H2 is also operated, being connected to negative battery over the contact of relay G2 and to positive battery over the wiper of selector D. Finally, relay K2 is operated, one of its terminals .being connected to negative battery over the contact of relay H2, and the other terminal being connected to positive battery over the second level brush of selector E. The armature of relay K2 is, therefore, held against its front or marking contact.

A circuit for the operating winding OWn may now be traced as follows: From negative battery over the marking contact of relay RR, over conductor iii, through the winding OWn of relay TR, over conductor I2, front contact of relay K2, second contact of distributor TD, over the brush of the distributor to the long segment i6 of the inner ring of the distributor, thence over conductor I'I, and through the holding Winding HWr to ground. This current will pass through the winding HWr in such a direction as to hold the Contact of the receiving relay RR against its negative or marking contact so long as the brush in the distributor rests upon segment number 2. This prevents the succeeding received impulse, if in the opposite direction, from shifting the armature of the receiving relay to spacing until the distributor has completed the transmission of the resulting impulse to the sending circuit TLJhe current flow through the winding OW is in such a direction as to activate the armature 10 of the sending relay toward its negative or marking contact and a marking impulse is sent to the line.

If, however, the received impulse had been a spacing impulse, positive battery would have been connected to the operating winding OWn, and current would have flown through this winding in the opposite direction. Hence the controls exercised by relays RR and K2 would have been spacing in the former instance and marking in the latter instance. This would result in shifting the armature of the transmitting relay TR to its positive or spacing contact. The current through the holding HWr of the receiving relay RR would also be reversed and would, therefore, hold the armature of the receiving relay RR upon its spacing contact so long as the brush of the distributor is upon its contact number 2.

As the brush of the distributor TD leaves contact number 2, the holding Winding HWr of the receiving relay RR is deenergized, and relay RR is now free to respond to the third impulse of the Baudot code received from circuit RL. If we examine the circuit conditions in the third level of the series of switches, it will be evident that relays F3 and G3 are energized, but that relay H is deenergized. Since the brush of selector E ig on the positive contact of the third level, the relay K3 is connected to positive battery at both its terminals and is deenergized.

With this condition existing, if the third impulse of the Baudot code received from circuit RL is a marking impulse, a circuit will be completed when the brush of the distributor reaches the segment 3, from negative battery, over conductor I0, through operating winding OWp of relay TR, over conductor I3, back contact of relay K3, third segment of the outer ring of the distributor TD, over the brush to the long inner segment I6 of the distributor, and thence over conductor I'I, through the holding winding HWr of the receiving `relay RR to ground. The current owing through the Winding HWr is in such a direction to hold the armature of relay RR against its marking contact. Since the relay RR is in marking condition due to the third received impulse, and since the relay K3, which records the enciphering condition for this impulse, is in spacing condition, the current flows through the Winding OWp in such a direction as to impel the armature of the relay TR to its spacing contact so that a positive pulse is sent out to the line TL.

It will, ofcourse, be evident that if the third character impulse had been a spacing pulse, the armature of relay RR Would have been connected to positive battery and the current flow through the windings HWY and OWp would have been reversed. This would cause the holding Winding HWr to hold the armature of relay RR against its spacing Contact so long as the brush of the distributor is upon segment 3 of the distributor. The current through the operating winding OWp of relay TR would now be flowing in such a direction as to cause the armature of said relay to rest upon its marking contact, and a negative marking pulse would be sent to the line, both relay RR and relay K3 being at this time in spacing condition.

Similarly, when the brush arm reaches segment fi, if the fourth received impulse of the Baudot code is a marking impulse, it will be evident from inspection that relay K4 in the fourth level of the switches is also in marking condition and, therefore, the transmitting relay TR Will shift its armature to its `marking contact, if it is not a1- l'l' ready resting there. The circuit in, this instance will be from negative battery, over the armature of relay RR, through the upper operating window OWn, over conductor l2, front contact of relay K4, 4th segment of the distributor, and thence over ycircuit elements previously traced to the holding winding I-IWr. Obviouslyii the ith pulse of the Baudot code corresponding to the character to be enciphered happened to be a spacing impulse, Uthe current flow through the winding OW would be reversed and the armature of the relay TR-would be shifted to its spacing contact, so that a positive pulse would be sent over the outgoing line Finally, considering the fifth impulse of the received Baudot code, it will be evident from inspec'tion that relay K5 for the existing setting of the switches ls energized and, therefore, in marking condition. Consequently, if the 5th received impulse is a marking impulse, the current will flow through the upper operating winding OWn in such a direction as to shift the contact of the relay TR to its marking position to send out a negative pulse to the line TL. If the received impulse is a spacing pulse, however, the flow of current will be in the reverse direction, and the winding OWU will shift the armature of the relay TR to its spacing contact and send out a positive pulse to the line TL.

As soon as the wiper of the distributor TD leaves segment number 5 of the outer ring, winding HWlwill be deenergized and relay RR will'respend to the stopping impulse, which is always a marking impulse. The relay RR will, therefore, have its armature on its marking contact and a circuit will be completed from marking battery over said armature, over conductor I0, through the operating winding OWp of relay TR, over conductor E@ to the stop segment in the outer ring of the distributor, and thence over the brush to the long inner segment I6, from which point it proceeds over conductor I1 and through winding HWr to ground. So long as the brush is upon the stop segment, the holding winding HWI will hold the armature of the relay RR upon its marking contact to prevent it from responding to the succeeding starting impulse (if oneimmediately follows) before the cycle of operations is completed. Whiley the brush passes over the stoping segment,v the operating winding OWp of the relay TR shifts thearmature of said relay to its marking contact so that a negative stop impulse will be sent to the line TL. Since the holding winding HW@ receives current in such a direction as to tend to hold the armature ofY relay TR against itsv marking contact, the marking impulse sent tothe line will continue even after the brush of the distributor leaves the stop segment, and indeed, will be maintained until the succeeding start impulse sets up a new cycle of operation to encipher a new character. i

Coming back to the distributor TD, as the wiper leaves'the stop segment it will come to rest on the zero segment of the'outer ring engaging with the armature of the release magnet RM. Release magnet RM, however, will not be operated until the succeeding start impulse comes in from the circuit RL. The succeeding starting impulse, which is always a space impulse, will shift the armature of the relay RR to its spacing contact and operate the release magnet RM ,over conductors lil and I5, as previously described, to start a new cycle of operation.

Let us now return to the condition existing while the brush of the distributor TD was pass- 12 ing over the stop segment, andr thereby transmitting the stop impulse to the. line TL. During the entire rotationof the distributor. up 'tothis point the various selectors A,.B, C, D and Ewere all set at the positions illustrated in the drawings to impose upon the relays K1 to K5, inclusive, an enciphering combination for scrambling thereceived Baudotcode in accordance with the setting of the switches. Whenthe brush reaches the stop segment, however, a switch-controlling cam SC momentarily closes its contact and connects ground to conductor |78 and thence over the key Ka, over right-hand backY contact of relay Ar, through the winding of the step magnet Mo. to positive battery. StepV magnet Ms isenergized,

and as itv pulls up itsA armature, the pawl of the armature (not shown) is advanced to engage a newtoothin the stopping ratchet wheel of theselector A.

At its right-hand contact step magnet Ma opens the short circuit about the right-hand winding ofy relay A1 (which is also connected to conductor i3), so that relay-A1 is energized. At its righthand front contact relay A1 is locked up over its right-hand winding so lol-lg as the contact made by the cam SC remains closed.y When the relay Av1 locks up, it opens at its right-hand armature the rcircuit previously traced through the stepping magnet M11, whichv is released to advance to selector A one step so that all of its brushes now rest upon the 7th contact. The other selectors remain as before. As soon as the cam' `SC releases its contact the circuit over conductor I8 is opened and locked-up relay Al is deenergized so that the circuit of the stepping magnet Ma is prepared for a new stepping impulse, which will occur when the cam SC again closes its contact after another rotation of the distributor. y

With the selector A advanced to its seventh contact, a new scrambling condition is setup in each bank upon the relays K1 to K5inclusive. If we trace the circuits, it will be evident that in the ril-st level, in' accordance with the new setting, relays F1 and VCn will be energized, relay Hl will be deenergized, and relay K1Y willbeenerf gized to shift its armature to marking condition. Tracing through the circuits of the other levels, itV will be evident that relayKz will-be deenergized, relay K3 will be energized, relay Kl will be energized and relay K5 will be deenergized. Consequentlythe new scrambling code will be markspace-mark-mark-space, whereas the previous l, scrambling code was space-mark-space-markmark. In other words, in this instance each pulse of the group of live is reversed, except the 4th o'ne which is unchanged. This is due to the fact that in the lith levelY the wiper of' selector A passes from a 6th contact, which was negative to a 7th contact which is also negative, whereas the wipers of theV other levels of selector A all happened to pass from a contactof oneVV polarity to a contact of opposite polarity.

Vt will be noted .that` the 6th level of each of vthe selectors has a set of contacts which are connected through individual lamps to positive battery. With all of the selectors in the position vshown in the drawings the brush of the 6th bank of selector A is resting upon the 6th contact, and, therefore, the 6th lamp of the group associated with selector A willV glow, indicating that the selector is in its 6th position. At the same time the lower brush of selector B is on its 18th contact so that its 18th lamp glows.

lAlso the lower brush of selector o is onus 14thV contact and causes the 14th lamp in its group to glow while the lower brush of selector D is on its 20th contact causing the 20th lamp of that group to glow. Finally, the lower brush of selector E is upon its 14th contact so that the 14th lamp of the last group glows. These lamps indicate the setting of each of the switches. When, as above described, the selector A was advanced from its 6th to its 7th contact, its 6th lamp will be extinguished and the glowing of the '7th lamp will indicate the new setting of said selector. Similarly other changes in the setting of any of the selectors will be indicated by the appropriate lamps.

When selector A has finally been advanced to its 22nd contact, a circuit is completed over its lower brush and the 22nd contact of its 6th level, through the last lamp of the series, and thence over conductor I9, contact of key Kb, back contact of relay B1, through the winding of step magnet Mb to positive battery. Step magnet -Mb upon drawing up its armature advances its pawl to a new tooth of the stepping ratchet,

but it does not move the ratchet until the step magnet is deenergized, which occurs as soon as the relay B1 is locked up upon the opening of the short circuit of its winding by the right-hand contact of step magnet Mb. Selector B is, therefore, advanced from its 18th position to its 19th position. Thus we now have a condition where selector A is upon its 22nd position, selector B in its 19th position, while the other selectors remain in the position shown in the drawings.

As soon as the distributor DT completes another revolution to utilize the new setting, it

connects ground to conductor I8 again, therebyv advancing the selector A from its 22nd Dosition to its first position. The wiper of selector A in passing from its 22nd contact opens the locking circuit for the relay B1 of the selector B, which extended over conductor I9 and the 22nd contact of the lower contact of selector A to ground over the lower wiper of selector A. Relay B1 is restored to normal so that the step magnet Mb is now ready to receive a new impulse after the selector A has again been advanced step-by-step to its 22nd contact. In the meantime twenty-two new scrambling codes have been set up and utilized before the selector B is again advanced.

In a similar manner, when the selector B has been advanced to its 22nd contact, a circuit for step magnet Mc is established and selector C is advanced from its 14th to its 15th position. Each time the selector B is rotated the selector C is advanced to a new position until it finally reaches its 22nd position, when it causes the magnet Md to step the selector D from its 20th to its 21st position. Finally, after selector D is advanced to its 22nd position, stepping magnet Me of the selector E advances said selector from its 14th to its 15th position.

To recapitulate, each time the selector A is advanced twenty-two steps, selector B is advanced one step. Each time selector B is advanced twenty-two steps, selector C is advanced one step. Each time selector C is advanced twenty-two steps, selector D is advanced one step, and finally, each time selector D is advanced twenty-two steps, selector E is advanced one step. Thus it is necessary for selector D to rotate over each of its twenty-two steps twenty-two times before the selector E makes one complete rotation step-bystep. This multiplying of the steps necessary for any preceding selector to be advanced before a By operating any one of these keys the corre-I sponding selector may be advanced one step manually. If at any time, therefore, the sending operator desires to change arbitrarily to a new setting of the selectors which control the key, he will simply send a message to the receiving operator to inform him what the new setting is to be. Thereupon both operators will manipulate their keys Ka to Ke, inclusive, a proper number of times to advance each of the ve selectors A, B, C, D and; E to its new setting, after which communicationmay be resumed as before,

By arbitrarily resetting the enciphering arrangement from time to time before the succession of over ve million combinations repeats,

itself, it is possible to prevent repetition of the complete succession of scrambling characters, and

only such repetition of individual charactersy takes place as will inevitably occur even under;

random conditions. Obviously, since we only have thirty-two characters in ordinary teletypewriter operation, even when these characters follow each other in a random manner, each character will inevitably be repeated a large numberv of times in a total of 5,153,632 possibilities, and

we may even nd the same group of severalv characters repeated in the same order several times in Such a large range 0f possibilities. But even here these few repetitions will have no meaning to one attempting to break the cipher, be-

cause each time they will appear in a dierent environment of preceding and following characters.

It will, of course, be evident that the positive and negative connections to each of the contacts of each of the levels of the several selector switches should be determined onfa wholly arbitrary and random basis, so that the resulting' enciphering key will have a random base the sequence of which will not be repeated over 5.153,- 632 operations.

While this inventionhas been discussed in certain specic arrangements which are deemed de-.

sirable, it will be obvious that the general principles herein illustrated may be embodied in other rorganizations widely different from those illustrated without departing from the spirit of the invention as defined in the appended claims.

What is claimed is:

1. A system for transmitting messages com-l posed of characters in the form of Baudot code combinations, means to encipher or decipher said messages by combining the message code comblnations with successive cipher code combinations representing characters which are unrelated tosaid message characters either as to order, grouping, frequency of occurrence, or relationship to.

each other, means to produce said cipher code combinations including a plurality of multipoint switches having wipers movable from point to point of said switches, circuits controlled by said switches to produce key pulses, said pulse being of one character if an odd number of said.' switches rest upon marking points and being of.

opposite character if an odd number of said switches do not rest upon marking points, and.`

1.55 means acting after ya given message .character has 'been combined with key pulses to shift at leastV one :of said switches with respect to the others to produce a new cipher combination for scrambling a succeeding message character.

2. yA system `for transmitting messages composed of characters in the form of Baudet code combinations, 'means to encipher or `decipher said messages'by' `combining the message code combinations with successive cipher code combinations representing characters which are unrelated to said message-characters -either as to order, grouping, frequency of occurrence, or relationship to each other, means to produce said cipher code combinations including a plurality of multipoint switches having wipers movable from point to point of said switches, circuits controlled by said switches to produce key pulses, said pulse being of one character if an odd number of said switches` rest upon marking points and being of opposite character if an odd number of said switches ldo not rest upon marking points, means acting after a given'message character has been combined with key pulses to shift at least one of said switches with respect to the others to produce a new cipher combination for combining with 'a 'succeed-ing message character, and means to visually indicate the point at which each .switch is set.

3. lA system for transmitting messages composed of characters in the form of Baudot code combinations, means to encipher or decipher said messages by combining the message code com-4 binations with successive cipher code combina-v tions representing characters which are unrelated to said messagev ch-aracters either as to order, grouping, frequency of occurrence, orv relationship to each other, means to produce said cipher code combinations including a plurality of multipointV switches having wipers movable from point tofpoint of said switches, circuits controlled by said switches to produce key pulses, said pulse -being-of one character if al1-odd number of' said switches rest lupon marking peints and being of opposite character if an odd number of said switches rdo-not rest upon marking points, a distributor Vfor successively transmitting said key pulsesjtocombine them with corresponding character pulses, and means synchronized with said distributor to transmit a resetting pulse latter said key vpulses have Abeen transmitted to change the setting :of said switches with respect to. each other toproduce anew cipher combinationior combining with a succeeding message character.

4. A system for transmitting messages com-` posed vof characters inthe form of Baudot code combinations, means. to. encipher or decipher said messages by combining the message code combinatioI-is` withsuccessive cipher code combinations representing charactersl which 'arev unrelated to said message characters either as to orderr, .'grouping, frequency of occurrence, or `relationship. ito. each'` other, vmeans 'to produce said cipher code. .combinations .including .a 'plurality' of multipoint vswitches .having Wipers .movable 'from point'torp'oint of said; switches, circuits controlled byA said switches tozlproduce key pulses, said. pulse being' of one. character i-f an odd. .number of said switches rest upon marking points andv being of opposite lcharacter if an odd number of said' switches do noti-rest uponxmarking points, va distributor for .successively transmitting said key pulses to combine them with corresponding charactor pulses, means synchronized with said distributor to transmit a resetting Vpulse after said key pulses have been transmitted to change the setting of said switches with respect to each other to produce a new cipher combination for combining with a succeeding message character, and means independent of said resetting pulse and controllable at will to reset any or all of said switches to produce a desired relationship between them.

e 5. A system fortransmitting messages composed of characters in the form of Ba-udot code combinations, means to encipher or decipher said mes sages by combining the message code combinations with successive cipher code combinations representing characters which are unrelated to said message characters either as to order, grouping, frequency of occurrence, or relationship to each other, means to produce said cipher code combinations including a plurality of multipoint switches having wipers movable from point to point of said switches, circuits controlled by said switches to produce key pulses, said pulse being of one character if an odd number of said switches rest upon marking points and being of opposite character if an odd numberA of said switches do not rest upon marking points, a distributor for successively transmitting said key pulses to combine them with corresponding character pulses, means synchronized with said distributor to transmit a resetting pulse after said key pulses have been transmitted to change the setting of said switches with respect'to each other to produce a new cipher combination for combining with a succeeding message character, means independent vof said resetting pulse and controllable at will to reset any or all of'said switches to produce a desired relationship be-l tween them, and means torvisually indicate the point at which each set is set.

6. A system for transmitting messages com-V posed oi characters in the form of Baudet code combinations, means to encipher or decipher said messages by combining the message code combinations with successive cipher Ycode combinations representing characters which are unrelated to said message characters either as to order, grou-p-v ing, frequency of occurrence, or relationship to each other, means to produce said cipher code combinations vincluding a series of multipoint switches having wipers movable from point to point of said switches, each of said switches having its points activated to produce a marking or a spacing condition, circuits controlled by said switches to produce key pulses, said pulse being of one character if an odd number of said switches rest upon marking points and being of opposite character if an odd number of said switches do not rest upon marking points, and mea-nsracti-ng after a given message character has been combined with key pulses to shift at least one of' said switches with respect to the others to producef-a new cipher combination for' scrambling a succeeding message character.

"1. A :system Yfor transmitting messages composed of characters in the form of Baudet code combinations, means to encipher or decipher said messages by combining the message code combinations with successivey cipher code combinationsv representing characters which are unrelatedto said message characters either as to order, grouping, frequency of occurrence, or relationship to each other, means to produce said cipher code combinations including a series of multipoint switches having wipers movable from point to point of said switches, each of said switches having its points'activated to producefa marking or a spacing condition, circuits controlled by said switches to produce key pulses, said pulse being of one character if an odd number of said switches rest upon marking points and being of opposite character if an odd number of said switches do not rest upon marking points, means acting after a given message character has been combined with key pulses to shift at least one of said switches with respect to the others to produce a new cipher combination for combining with a succeeding message character, and means to visually indicate the point at which each switch is set.

8. A system for transmitting messages composed of characters in the form of Baudot code combinations, means to encipher or decipher said messages by combining the message code combi Ynations with successive cipher code combinations representing characters which are unrelated to said message characters either as to order, grouping, frequency of occurrence, or relationship to each other, means to produce said cipher code combinations including a series of multipoint :switches having wipers movable from point to point of said switches, each of said switches having its points activated to produce a marking or a spacing condition, circuits controlled by said switches to produce key pulses, said pulse being of one character if an odd number of said switches rest upon marking points and being of opposite character if an odd number of said switches do not rest upon marking points, a distributor for successively transmitting said key pulses to combine them with corresponding character pulses, and means synchronized with said distributor to transmit a resetting pulse after said key pulses have been transmitted to change the setting of said switches with respect to each other to produce a new cipher combination for combining with a-succeeding message character.

9. A system for transmitting messages composed of characters in the form of Baudot code combinations, means to encipher or decipher said messages by combining the message code combinations with successive cipher code combina--V tions representing characters which are unrelated to said message characters either as to order, grouping, frequency of occurrence, or relationship to each other, means to produce said cipher code combinationsl including a series of multipoint' switches having wipers movable from point to point of said switches, each of said switches having its points activated to produce a marking or a spacing condition, circuits controlled by said switches to produce key pulses, said pulse being' of one character if an odd number of said switches rest upon marking points and being of opposite character if an odd number of said switches do not rest upon marking points, a distributor for successively transmitting said key pulses to Combine them with corresponding character pulses, means synchronized with said distributor to transmit a resetting pulse after said key pulses have been transmitted to change the setting of said switches with respect to each other to produce a new cipher combination for combining with a succeeding message character, and means independent of said resetting pulse and controllable at will to reset any or all ofsaid switches .to produce a desired relationship betweenthem. 10. A system for transmitting messages coniposed of characters in the form of Baudot code combinations, means to encipher or decipher said messages by combining the message code combinations with successive cipher code combinations representing characters which are unrelated to said message characters either as to order, grouping, frequency of occurrence, or relationshipto each other, means to produce said cipher code combinations including a series of multipoint switches having wipers movable from point to point of said switches, each of said switches having its points activated to produce a marking or a spacing condition, circuits controlled by said switches to produce key pulses, said pulse being of one character if an odd number of said switches rest upon marking points and being of opposite character if an odd number of said switches do not rest upon marking points, a distributor for successively transmitting ksaid key pulses to combine them With corresponding `char-- acter pulses, means synchronized with said distributor to transmit a resetting -pulse after said key pulses have been transmitted to change the setting of said switches with respect to each other to produce a new cipher combination for combining with a succeeding message character, means independent of said resetting pulse and controllable at will to reset any or all of said switches to produce a desired relationship between them, and means to visually indicate the point at which each switch is set.

11. A system for transmitting messages composed of characters in the form of Baudot code combinations, means to encipher or Vdecipher said messages by combining the message code combinations with successive cipher code combinations representing characters which are unrelated to said message characters either as to 0rder, grouping, frequency of occurrence, or relationship to each other, means to produce said cipher code combinations including a series of multi-point switches having wipers movable from point to point of said switches, a set of circuit connections related to each of a plurality of points of one of said switches extending to eachof a plurality of points of a second of said switches,`a set of circuit connections related to each of said plurality of points of said second switch being ex-V tended to each of a plurality of points of a third switch'when provided, and sets of circuit connections in a similar manner being extended to succeeding switches when provided, character determining elements associated with the last switch of said series, said character determining elements being activated in accordance with the circuits thus extended from switch to switch in the series, means to combinethe key pulses formed by said character determining elements with the pulses corresponding to message characters, and means acting after a given message character has been thus treated to shift at least one of said switches with respect to the others to produce a new cipher combination for combining with a succeeding message character.

12. A system for transmitting messages composed of characters in the form of Baudot code combinations, means to encipher or decipher said messages by mixing the :message code combinations with successive ciphervcode combinations representing characters which are unrelated to said message characters either as to order, grouping, frequency of occurrence, or relationship to each other, means to produce said cipher code combinations including a series of multipoint switches having wipers movable from point to point of said switches, a set of circuit connections ami-,507

-19 points of a second of said Switches, a set 'ci circuit connections related to each of said plurality of points of said second switch being extended to each of a plurality of points of a Vthird switchwhen provided, and sets of circuit connectionsvin a similar manner being extended to succeeding switches when provided, character determining elements associated with the last switch of said series, said character determining elements being activated in accordance with the circuits thus 'extended from switch to switch in the series,

'means to combine the key pulses formed by said character determining elementswith the pulses corresponding to message characters, means acting after a given message character has been so treated to shift at least one of said switches with respect to the others to produce a new cipher combination for combir'iing with a succeeding message character, and means to visually indicate the point at which each' switch is sett 13. A system for transmitting messages composed of characters in the vform of Baudet code combinations, means to encipher or 'decipher 'said messages by combining the message code combinations with successive cipher code combinations representing characters which are unrelated to said message characters either as to order, grouping frequency of occurrence, or relationship to each other, means to produce said cipher 'code combinations including a series Yci multipoint switcheshaving' wipers movable Vfrom point to point of said switches, a set of 'circuit connections relatedto each of alplurality of points of one of said lswitches extending to each of a plurality of vpoints of va second of said switches, a

set of circuit connections related to each of said plurality of points of said 'Second switch being extended to each of a plurality of points of a third switch when provided, and sets of circuit connections in a similar manner being extended to succeedingswitches when provided, character determining elements associated with the last switch of said series,l said character determining elements being activated in accordance with the circuits thus extended rfrom switch to switch*V in the series, means to'combine the key pulses formed by said character determining elements with the pulses corresponding to message characters, a distributor for successively vtransmitting said key pulses tocombine -them withcorrespending message character pulses and means synchronized withsaid distributor to transmita resetting pulse after said key pulses lhave been transmitted to change ythe'setting lof said switches with respect to each other to produce a newv cipher combination for combining rwith 'fa succeeding message character.

14. A system for transmitting messages ccmposed of characters inthe form of VBaudot code combinations, 'means to encipher or decipher vsaid messages by combining the message code combinations with successive cipher code combinations representing characters which are unrelated to said message characters either as to order, grouping, frequency of occurrence, or relationship to each other, means to produce said cipher code combinations including a series of multipoint switches having wipers movable vfrom point to point of said switches, a set ofcircuit connections related to each of a lplur'ality of' points of one of said switches extending to each of a plurality of pointsv of a second of said switches, a set of circuit connectionsl related to each .of said plurality of points of said second switch being extended to each of a plurality of'points ofA` 20 a thi-rd switch when provided, and sets of circuit connections in a similar manner being extended to succeeding switches when provided, character determining elements associated with the last switch of said series, said character determining elements being activated in accordance with the circuits thus extended from switch to switch in the series, means to scramble the key pulses formed by said character determining elements with the pulses corresponding to message characters, a distributor for successively transmitting said key pulses to combine them with corresponding message character pulses, means' synchronized with said distributor to transmit a resetting pulse after said key pulses have been transmitted to change the setting of said switches with respect to each otherY to produce a new cipher combination for combining with a succeeding message character, and means independent of saidresetting pulse and controllable at will to reset any or all of said switches to produce a desired relationship between them.

15. A system for transmitting messages composed of characters in the form of Baudet code combinations, means to encipher or deciphersaid messages by co-mbining the message code combinations with successive cipher code combinations representing characters which are unrelated to saidy message characters either as to order, grouping, frequency of occurrence, yor relationship to each other, means to produce said cipher code combinations including a'series of multipoint switches having wipers movable -from -pcirit, to point of said switches, a set of circuit connections related to each of a plurality ofpoints of one of said switches extending to each of a vplurality of points of a second of said switches, a set of circuit connections related't'o each of 'said plurality of points of said second switch being extended to each of a plurality of points of a third switch "when provided, and sets of circuit connections in a similar manner being extended to succeeding switches when provided, character determining elements associated with ythe last switchof said series, said character determining elements being activated in accordance with the circuits thus extended from switch to switch in the series, means to combine the key pulses formed vby said character determining elements'with the pulses corresponding to message characters, a distributor for successively transmitting said key pulses to combine them with corresponding message character pulses, means synchronized with vsaid distributor to transmit a resetting pulse after said key pulses have'been transmitted to change the setting of said switches with respect to each other to produce a new cipher combination 4for combiningr with a succeeding message character, means independent of said resetting pulse and controllable at will to reset any or all of said switches to produce a desired relationship between them, and means to visually indicate the point at which each switch is set.

16. A system for transmitting messages .composed of characters in the form of Baudet code combinations, means to encipher or decipher said messages by combining the message code combinations with successive cipher-code combinations representing characters which are unrelated to said message characters either as to ordeiigrouping, frequency of occurrence, or relationship to other, means to produce'said cipher code combieach other, means to produce said cipher code combinations including a series of switching stages, each of said stages having a plurality of terminals,

-21 a set of character determining elements one co1- responding to each unit of the Baudot code, said character determining element being associated with separate terminals of a final Switching stage of the series, a set of interstage conductors rer lated to terminals of the next preceding stage, said conductors leading toterminals of said iinal switching stage, and sets of interstage conductors related to terminals of still earlierk stages when provided, each such set leading to terminals of the next succeeding stage, the number of conductors in each interstage set being evenly divisible bythe number of said character determining elements, said character determining elements being activated in accordance with circuits extended from stage to stage in the series, means to combine the key pulses formed by said character determining elements with the pulses corresponding to message characters, and means acting after a given message character has been combined with key pulses to shift the connections of at least one of said sets of interstage conductors with respect to the'other sets to produce a new cipher combination for combining Iwith a succeeding message character.

1'7. A system for transmitting messages cornposed of characters in the form of Baudot code combinations, means to encipher or decipher said messages by combining the message code combinations with successive cipher code combinations representing characters which are unrelated to said message characters either as to order, grouping, frequency of occurrence, or relationship to each other, means to produce said cipher code combinations including a series of switching stages, each of said stages having a plurality of terminals, a set of character determining elements one corresponding to each unit of the Baudot code, said character determining element being associated With separate terminals of a nal switching stage of the series, a set of interstage conductors related to terminals of the next preceding stage, said conductors leading to terminals of said final switching stage, and sets of interstage conductors related to terminals of still earlier stages when provided, each such set leading to terminals of the next succeeding stage, the number of conductors in each interstage set being evenly divisible by the number f said characterdetermining elements, said character determining elements being activated in accordance with circuits extended from stage to stage in the series, means to ccmbine the key pulses formed by said character determining elements with the pulses corresponding to message characters, means acting after a given message character has been combined with key pulses to shift the connections of at least one of said sets of interstage conductors with respect to the other sets to produce a new cipher combination for combining with a succeeding message character, and means to visually indicate the point to which each 'switching stage is so shifted.

18. A system for transmitting messages composed of characters in the form of Baudot code combinations, means to encipher or decipher said messages by combining the message code combinations with successive cipher code combinations representing characters which are unrelated to said message characters either as to order, grouping, frequency of occurrence, or relationship to each other, means to produce said cipher code combinations including a series of switching stages, each of said stages having a plurality of terminals, a set of character determining ele- 22 ments one corresponding to each unit ofl the Baudot code, said character determining element being associated with separate terminals of a final switching stage of the series, a set of interstage conductors related to terminals of the next preceding stage, said conductors leading to terminals'of said i'lnal switching stage, and sets of interstage conductors related to terminals ofstill earlier stages when provided, each such set leading to terminals of the next succeeding stage, the number of conductors in each interstage set being evenly divisible by the number of said character determining elements, said character determining elements being activated in accordance with circuits extended from stage to stage in the series, means to combine the key pulses formed by said character determining elements with the pulses corresponding to message characters, a distributor 4for successively-transmitting'said key pulses to combine them with corresponding message character pulses, and means synchronized with said distributor to transmit a resetting pulse after said key pulses have been transmitted to change the connections of at least one of said sets of interstage conductors with respect to the other sets to produce a new cipher combination for combining with 'a succeeding message character.

19. A system for transmitting messages composed of characters in the form of Baudot code combinations, means to encipher or decipher said messages by combining the message code combinations with successive cipher code combinations representing characters which are unrelated to said message `characters either as to order, grouping, frequency of occurrence, or relationship to each other, means to produce said cipher code combinations including a series of switching stages, each of said stages having a plurality of terminals, a set of character determining elements one corresponding to each unit of the Baudot code, said character determining element being associated with separate terminals of a nal switching stage of the series, a set of interstage conductors related to terminals of the next preceding stage, said conductors leading to terminals of said nal switching stage, and sets of interstage conductors related to terminals of still earlier stages when provided, each such set leading to terminals of the next succeeding stage, the

number of conductors in each interstage set being evenly divisible by the number of said character determining elements, said character determining elements being activated in accordance with circuits extended from stage to stage in the series, means to combine the key pulses formed by said character determining elements with the pulses corresponding to message characters, a distributor for successively transmitting said key pulses to combine them with corresponding message character pulses, means synchronized with said distributor to transmit a resetting pulse after said key pulses have been transmitted to change the connections of at least one of said sets of interstage conductors with respect to the other sets to produce a new cipher combination for combining with a succeeding message character, and means independent of said resetting pulse and controllable at Will to reset any or all of the connections of said sets of interstage conductors to produce a desired relationship between them.

20.A system for transmitting messages composed of characters in the form of Baudot code combinations, means to encipher or decipher said messages by combining the message code combinations with successive cipher code combinations representing. characters whichare unrelated Vto said message characters4 either 'as 'to'order grouping, frequency of occurrence; orrelationship 'men't being associated with separate terminals 'of Y'a' nal' switching stagefof4 the series', a setfoil interstageccnductors related toterminals of. 'the next preceding stage, said-conductorsfleading lto terminalsof `said iinalrswitching stage,` and'sets 'of interstage Aconductors relatedlto terminals of 'still rearlier stag-'es when provided', each-suchset leading to terminals yof the nextfsucceeding stage, the number of conductors in ze'ach'interstage set being evenly dvisiblebythe `numbcr'of` said' character determining' elements, said characterdetermining elements being `activated 2in' Aaccordan'cetvith circuits extended from sta-ge to vstage -in thevseries, means tocombine the key pulses `formed by said character determining elements with the pulses corresponding to message charac ters, a distributor for successively transmitting said key pulses'to combine them Withcorresponding message character pulses, means synchronized with said distributor to transmit a resetting pulse after said key pulses have been transmitted' to vchange the connections of at. least one of said sets of interstage conductors with respect to the yother sets to produce a new cipher combination forcombining with a succeeding message character, means independentof -said resetting pulse and controllable at will to reset'any or all of the connections of said sets'cf interstage conductors to produce a desired relationship between them, and means to visually indicate the reset' condition of said connections. v f

DONALD B.l PERRY. v 

